MICA    DEPOSITS    OF    WESTERN    NORTH    CAROLINA. 
413 
appears  as  alternating  portions  of  more  or  less  translucent  and  white 
quartz.  Small  mica  plates  lie  in  certain  streaks  or  seams  parallel  to 
this  banding.  Under  the  microscope  a  thin  section  proved  to  be 
almost  entirely  composed  of  rather  fine-grained  quartz.  The  grains 
are  angular  and  fit  somewhat  closely  together.  Some  of  them  show 
evidence  of  moderate  strain.  Between  crossed  nicols  a  slight  banding 
is  apparent  in  certain  directions  by  the  extinction  of  the  quartz 
grains.  Parallel  to  this  banding  are  two  streaks  of  minute  black  par- 
ticles, probably  magnetite.  These  lie  chiefly  between  separate  grains 
of  quartz,  though  some  are  included  in  the  quartz  grains.  The  quartz 
contains  many  inclusions.  Some  of  them  seem  to  be  irregular  cavi- 
ties, with  or  without  gas;  others  have  a  reddish  color,  and  may  be  iron 
oxide  which  has  worked  its  way  from  the  pores  between  the  grains  into 
the  cavities  in  the  quartz. 
Fig.  15.     Pegmatite,  2i  feet  thick,  at  Wayah   Bald  mine,  Macon  County,  N.  C.     1,  Wall  rock  (mica 
•  gneiss);  2,  pegmatite,  mostly  feldspar,  quartz,  and  mica;  3,  quartz. 
The  mica  was  reported  to  be  plentiful  in  the  feldspar-quartz  streak 
between  the  quartz  band  and  the  wall  rock.  The  color  is  a  beautiful 
"rum"  and  the  quality  excellent. 
In  the  other  two  mines  the  pegmatite  cuts  the  mica-gneiss  country 
rock,  as  in  the  Lyle  Cut.  There  is  also  a  regular  quartz  vein  within 
the  pegmatite.  The  mica  occurs  in  a  matrix  consisting  mostly  of 
feldspar  with  some  quartz,  between  the  quartz  band  and  the  walls. 
In  the  Wayah  Bald  mine  the  quartz  forks  in  one  place,  nearly  inclosing 
a  small  mass  of  feldspar  (see  fig.  15),  and  in  another  part  it  completely 
envelops  a  mass  of  feldspar  3  or  4  inches  thick.  Banding  of  the  quartz 
was  not  observed  in  the  Wayah  Bald  mine.  Both  mines  produce 
"  rum  "-colored  mica  of  the  same  excellent  quality  as  that  of  the  Lyle 
Cut. 
All  are  old  mines  except  the  Wayah  Bald,  which  is  the  only  one  that 
has  been  worked  recently.     It  shut  down,  however,  in  the  fall  of  1906. 
Bull.  315—07 27 
